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SCANDIR(3)                 Linux Programmer's Manual                SCANDIR(3)



NAME
       scandir, alphasort, versionsort - scan a directory for matching entries

SYNOPSIS
       #include <dirent.h>

       int scandir(const char *dirp, struct dirent ***namelist,
              int (*filter)(const struct dirent *),
              int (*compar)(const struct dirent **, const struct dirent **));

       int alphasort(const void *a, const void *b);

       int versionsort(const void *a, const void *b);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       scandir(), alphasort(): _BSD_SOURCE || _SVID_SOURCE
       versionsort(): _GNU_SOURCE

DESCRIPTION
       The  scandir()  function scans the directory dirp, calling filter() on each directory entry.  Entries for which
       filter() returns non-zero are stored in strings allocated via malloc(3), sorted using qsort(3) with the compar-
       ison  function  compar(), and collected in array namelist which is allocated via malloc(3).  If filter is NULL,
       all entries are selected.

       The alphasort() and versionsort() functions can be used as the comparison function compar().  The former  sorts
       directory   entries  using  strcoll(3),  the  latter  using  strverscmp(3)  on  the  strings  (*a)->d_name  and
       (*b)->d_name.

RETURN VALUE
       The scandir() function returns the number of directory entries selected or -1 if an error occurs.

       The alphasort() and versionsort() functions return an integer less than, equal to, or greater than zero if  the
       first argument is considered to be respectively less than, equal to, or greater than the second.

ERRORS
       ENOMEM Insufficient memory to complete the operation.

VERSIONS
       versionsort() was added to glibc in version 2.1.

CONFORMING TO
       alphasort()  and  scandir()  are  specified  in POSIX.1-2008, and are widely available.  versionsort() is a GNU
       extension.

       The functions scandir() and alphasort() are from 4.3BSD, and have  been  available  under  Linux  since  libc4.
       Libc4 and libc5 use the more precise prototype

           int alphasort(const struct dirent ** a,
                         const struct dirent **b);

       but glibc 2.0 returns to the imprecise BSD prototype.

       The function versionsort() is a GNU extension, available since glibc 2.1.

       Since glibc 2.1, alphasort() calls strcoll(3); earlier it used strcmp(3).

EXAMPLE
       #define _SVID_SOURCE
       /* print files in current directory in reverse order */
       #include <dirent.h>

       int
       main(void)
       {
           struct dirent **namelist;
           int n;

           n = scandir(".", &namelist, 0, alphasort);
           if (n < 0)
               perror("scandir");
           else {
               while (n--) {
                   printf("%s\n", namelist[n]->d_name);
                   free(namelist[n]);
               }
               free(namelist);
           }
       }

SEE ALSO
       closedir(3),  fnmatch(3),  opendir(3),  readdir(3),  rewinddir(3),  seekdir(3),  strcmp(3), strcoll(3), strver-
       scmp(3), telldir(3)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                               2009-02-10                        SCANDIR(3)